Breaking the ice: Annual ‘cutting the keys’ gets underway on the Rideau

Snow blowers were out in full force Monday on the frozen Rideau River, as city crews began preparing for spring flood prevention. Before they start the annual icebreaking program, crews must clear the snow off the top of the Rideau River. The City of Ottawa is in charge of the work, with the help of the Rideau Valley Conservation Authority, which has environmental protection responsibilities for the Rideau Valley watershed.

OTTAWA — Snow blowers were out in full force Monday on the frozen Rideau River, as city crews began preparing for spring flood prevention.

Before they start the annual icebreaking program, crews must clear the snow off the top of the Rideau River. The City of Ottawa is in charge of the work, with the help of the Rideau Valley Conservation Authority, which has environmental protection responsibilities for the Rideau Valley watershed.

The program route begins at the dam right off the Sussex bridge and ends at Hog’s Back, following a nine-kilometre stretch of water.

How it works:

There are two stages to icebreaking, one of which has already started, said Bruce Reid, director of watershed engineering and science for the conservation authority.

“First thing they do is they take these large saws out on the river, and they cut … long slots in the direction of flow in the ice,” Reid said. “These slots are like parallel lines running under bridges and over some utility crossings, whether it’s telecommunications cables or sewer lines or water lines that run under the river.”

Reid said “the cutting of the keys” is done after city crews have removed the snow from the ice.

The next stage of ice removal uses an amphibious excavator — the “amphibex” — which Reid said looks like a giant crab climbing on top of the ice.

It uses different attachments to break up the ice. “It’s sort of like a hydraulic excavating machine that’s mounted on pods that enable it to float on the water and allow it to climb around,” he said.

Reid said the machine can climb onto the edge of an ice sheet, and the weight is often enough to break it.

“They use the amphibex to loosen up the ice on the Ottawa River below the Rideau Falls, and then they move it up onto the river. Usually this happens in early March where they start at the downstream end of the Rideau and work their way progressively upstream.”

City crews may also blast the ice with explosives if needed. Ice-breaking operations continue daily until the river flow is stabilized, according to the city’s website.

Jason Staniforth, manager of core roads for the city of Ottawa, said the city began using the amphibex machine on a trial basis in 1992.

“That comes in and breaks up around the base of the falls around the Ottawa River, and then we take it out of the water and bring it up onto the Rideau River itself, and that does the majority of the ice breaking now.”

Reid said that the ice removal process depends on having enough river flow to move the ice once it’s broken.

“(City crews) know enough now about the process that it takes a certain amount of natural run-off or flow in the river just to move things out onto the Ottawa River, otherwise the ice just sits there and slows their progress,” he said.

“So it’s about watching the weather, watching the river conditions, and moving when things seem appropriate.”

Why do this?

The only reason for icebreaking, Reid said, is to prevent flooding.

“When you look into the old newspaper accounts — even as far back as the early 1900s — there would be ice jams on the river when spring comes, and the snow melts, and the river flows rise,” he said.

“So, in the early days it was done just in reaction to flooding … In the midst of ice jams, they’d be sending men and equipment out to try and break up the broken ice and alleviate the flooding that had already occurred.”

Reid said it wasn’t until the 1930s or ’40s that the city started icebreaking as a preventive measure.

Staniforth said the icebreaking program follows a route that “historically” experiences backups, due to flooding from the Rideau River flood plain.

He said there are about 900 structures along the 3,800-square-kilometre watershed that would be at risk of damage if the city didn’t undergo this program every year.

Environmental concerns

The Rideau Valley Conservation Authority became involved with the program in a liaison role in the early 1990s, Reid said.

“We’ve always run a flood forecasting and warning service, so we’re watching watershed conditions and the weather and making predictions on when flows will rise and how high,” he said.

Up until that point, the city was completely in charge of the icebreaking program, and paid for it using entirely municipal funding. Reid said that once the conservation authority got involved, the city was able to secure provincial funding through the Ministry of Natural Resources.

“It’s in the order of $100,000 a year that we can flow to the city from the province through the conservation authority’s involvement,” Reid said.

Staniforth said that the actual amount received is slightly higher, and that the program costs about $500,000 in total.

In the mid-1990s, the conservation authority also commissioned an independent review of the icebreaking program to look at its environmental consequences. Ultimately, it found that the program was necessary to prevent property damage and public safety problems, according to Reid.

It also called for the use of the amphibious excavator when possible, and less frequent use of explosives.

Staniforth said the amphibex machine combined with key-cutting has helped the city use fewer explosives, thereby lessening the environmental impact of the program.

“Really, the blasting that’s done is at the falls right between the Sussex bridge and the dam, and then leading back to the next set of bridges, and essentially it’s just because there’s no way to put the boat into the water, the amphibex machine into the water to break up the ice.”

The ice-blasting and removal program was also featured on the BBC documentary series, The Human Planet.

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